This study investigates the possible gain and limitation by performing colonoscopy and double-contrast enema immediately after, and every six months after, radical surgery for colorectal cancer. It was possible to perform a complete colonoscopy within three months of surgery in 80 per cent of the 239 patients and at the follow-up time in 90 per cent. Incompleteness was related to insufficient bowel preparation, narrow anastomosis, and long transverse colon. Five patients had synchronous cancers, and 64 had adenomas at the time of surgery. The risk of recurrent adenomas in the latter was higher (17/64) than in those without adenomas (15/175). The adenomas were located above the rectum in 57 of 80 patients who had polypectomy. Four patients with metachronous cancer and one of five patients with local recurrence had another radical operation, while this was possible in none of 40 patients with recurrence diagnosed by other means than colonoscopy and enema. Radical colorectal surgery should be followed by colonoscopy and double-contrast enema, but how often and for how long remains to be established.